Attention mainly will be focused on three previously documented potentially exploitable peculiarities of folate-related metabolism in adult filariae: (1) their ability to use 5-methyltetrahydrofolate (5-methy1FH4), the major form of folate they encounter in their mammalian hosts, by oxidizing this otherwise inactive metabolite to 5,10-methyleneFH4; (2) their apparent complete dependence upon the de novo synthesis of thymidylate; and (3) their inability to synthesize methionine from homocysteine so that they must rely upon host-provided methionine. We shall attempt to induce a severe folate-deficiency state in adult filariae in vivo by administering to their hosts a combination of menoctone, which can block their utilization of 5-methylFH4, and methotrexate, a folate analog that strongly inhibits dihydrofolate reductase consequently inhibiting the regeneration of FH4. We shall determine whether a new methionine antagonist, L-2-amino-4-methoxy-trans-3-butenoic acid, which is relatively non-toxic to mice, can adversely affect adult filariae in vitro and in vivo, and if it can, we shall determine its mechanism(s) of action. We shall determine whether 5-methyltetrahydrohomofolate, a folate analog that inhibits filarial thymidylate synthetase and other folate-related enzymes and that also can compete with 5-methy1FH4 for uptake, can lead to the sterilization of the parasites in vivo or otherwise adversely affect them. Our recent finding that adult Brugia pahangi and Dirofilaria immitis synthesize dolichols and that they possess a dolichol phosphate-stimulated microsomal glycosyl transferase system that is associated with glycoprotein synthesis has revealed a hitherto unexplored aspect of filarial metabolism that merits further investigation. We shall further delineate the pathway of glycoprotein synthesis in adult filariae, attempt to identify the classes of filarial glycoproteins and the nature of their sugar components, and to determine whether they are located exclusively subcuticularly or whether they are also present on the cuticular surface as sheddable macromolecules. The long-term objective of the project is to continue the attempt to discover metabolic differences between adult filariae and their mammalian hosts which might be feasibly exploited for antifilarial chemotherapy.